DESCRIPTION: A key variable affecting the public and private health care system of the U.S. and other industrialized countries is the current trend in age-specific mortality rates, especially the trend at older ages. Most of the increase in life expectancy over the past 200 years has been due to dramatic reductions in mortality at younger ages, while death rates at older ages have fallen much less rapidly. It now appears that this situation may be changing, however, and the changes we are now observing may have enormous implications for the future size and composition of the elderly population. Will the trend toward higher life expectancy continue in the next century? Clearly, no one can predict the future with certainty. Rather, this project seeks to answer a more limited set of questions: Has the age pattern of mortality decline held constant over time, as assumed in many projection methods, or has it been changing? Has the shape of the human survival curve become more "rectangular" over time? Has the human lifespan been rising over time, or does it appear to be reaching some biological limit? The answers to all of these questions have important implications for the assumptions employed in mortality projections for the U.S. and other developed countries. A unique aspect of this application is its emphasis on a balanced examination of both cohort and period trends in mortality. To achieve this objective, a new cohort mortality data archive will be assembled, containing high-quality cohort and period life tables (and the raw data used to compute them) for a collection of at least 10 developed countries. These data will be made available to other researchers through the World Wide Web.